"The findings suggest that regular, high-level intake of resveratrol - a compound found in red wine and dark chocolate - may convey protective effects on cognitive functions, a hypothesis that now needs to be evaluated in large-scale clinical trials," Veronica Witte, a neuroscientist at the Charite-Universitatsmedizin Berlin in Germany, was quoted as saying.

In a study involving overweight adults, those who took resveratrol supplements for six months had better short term recall than their counterparts who took a placebo. The people who took the supplement also had more connections among brain areas involved in memory.

Aside from red wine and dark chocolate, sources of resveratrol include red grapes, peanuts, blueberries and Japanese knotweed.

In the new study, Witte and her colleagues tested 46 participants who were overweight but otherwise healthy.

Half of the volunteers were randomly assigned to take 200 milligrams of resveratrol daily for six months. Those who received resveratrol supplements remembered more words on a list that they had seen 30 minutes previously than those who received the placebo.